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Antarctica’s Blood Falls are a sign of life below ground

By Colin Barras

The iron in the water gives Blood Falls their name

(Image: Peter Rejcek, National Science Foundation)

Video: Airlifted sensor finds hidden water in Antarctica

Antarctica’s Blood Falls are well named. There, the white tongue of the Taylor Glacier is stained crimson, as if the ice itself has been wounded. The iron in the water – which oxidises to give the falls their vivid red colour – comes from the weathering of the bedrock beneath the ice, a process enhanced by microbial action.

“This unique feature is much more than a curiosity – it is a portal into the Antarctic subsurface, a hint at what lies beneath,” says Jill Mikucki at the University of Tennessee in Knoxville.

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We already know that there is liquid water – and life – in some of the lakes beneath Antarctica’s ice. Blood Falls is a sign of something else&colon; that the ground, too, holds liquid water, and that it may have extensive microbial activity. The falls are perhaps the only place where this groundwater comes to the surface. They flow just a few times a decade, possibly driven by changes in the weight of the ice above.

Now a study by Mikucki and her colleagues has found this groundwater could be surprisingly extensive. They used an electromagnetic sensor attached to a helicopter to map electrical resistivity in the relatively ice-free Taylor Valley, to the east of Blood Falls.

Resistivity shoots up by several orders of magnitude when soil water freezes. So by looking for areas of the valley where resistivity readings were low, the team could map the extent of the sub-surface water. Their results revealed large bodies of liquid in ground 185 metres below the surface, forming aquifers that stretch down the valley and apparently into the Ross Sea, a deep bay of the Southern Ocean.

“This may be the most different of all liquid water reservoirs on Earth since it is not directly replenished by infiltrating rainwater or seasonal snowmelt,” says Slawek Tulaczyk at the University of California, Santa Cruz. “It certainly is the least understood component of hydrological system on our planet, because it is hidden beneath either permafrost or the ice sheet.”

“It is becoming clear that water stored in the unfrozen ground beneath the Antarctic Ice Sheet comprises a very large groundwater reservoir,” says Poul Christoffersen at the University of Cambridge, who wasn’t involved in the research. “But we don’t know much about this reservoir.”

Tulaczyk says that there is no reason why similar groundwater bodies should not exist elsewhere beneath Antarctica.

The groundwater is cold, deep and twice as salty as seawater, but the water streaming out of Blood Falls, which teems with microbes, tells us that it is unlikely to be lifeless. “The fact that the [water] contains metabolically active micro-organisms that appear to be suited to life in a dark, cold brine supports the idea that life should persist throughout the subsurface,” says Mikucki.

If so, those microbes could be fuelling life in the Southern Ocean. By breaking down iron-containing rocks they might be dumping as much as 170 million kilograms of iron into the ocean each year, according to the researchers’ estimates, helping to explain why marine productivity is seasonally very high near to the coast.

However, we don’t yet know whether this happens, cautions Mark Moore at the University of Southampton, UK – the iron might simply react and be lost where the groundwater meets the sea.